Compressor installation with drying device for compressed gas and method for drying compressed gas

ABSTRACT

A compressor installation with drying device for compressed gas, with the drying device containing a housing with a drying zone and a regeneration zone; where in the housing a drying agent is provided; and where the pressure line includes a heat-exchanger for cooling the compressed gas before it enters the drying zone. A tap-off pipe is connected to the discharge line that is connected to a cooling inlet of the heat-exchanger, while the heat-exchanger further includes a cooling outlet that is connected to the inlet of the regeneration zone, while the outlet of the regeneration zone is connected to the pressure line.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 15/784,890, filed Oct. 16, 2017, which claims the benefit of Belgiumapplication BE 2016/5804, filed Oct. 25, 2016, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention concerns a compressor installation with a dryingdevice for compressed gas, with the compressor installation having acompressor element with an outlet for compressed gas to which a firstend of a pressure line is connected; whereby said drying device has ahousing with inside it a drying zone with a first inlet for compressedgas to be dried, to which a second end of said pressure line isconnected in such a way that the full flow rate of compressed gasoriginating from said compressor element is transported to the dryingzone; and whereby said drying zone further comprises a first outlet fordried, compressed gas to which a discharge line is connected; whereby insaid housing a regeneration zone is also provided with a second inletfor the supply of a regeneration gas, and a second outlet for thedischarge of used regeneration gas; whereby in the housing of the dryingdevice a drying agent can be successively moved through said drying zoneand the regeneration zone; and whereby said pressure line includes aheat-exchanger for cooling the compressed gas before it enters saiddrying zone.

A disadvantage of known compressor installations provided with a dryingdevice is that a considerable cooling capacity is required to make thetemperature of the gas to dry low enough to obtain efficient drying inthe drum.

Dryers for compressed gas with a rotatable desiccant drum containingdrying agent are already known and are for example described in WO01/87463, WO 02/38251, WO 2007/079553, U.S. Pat. No. 5,385,603 and theU.S. Pat. No. 8,349,054.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an improved and/oralternative compressor installation.

To this end the invention concerns a compressor installation with adrying device for compressed gas, with the compressor installation beingequipped with a compressor element with an outlet for compressed gas towhich a first end of a pressure line is connected; whereby said dryingdevice is provided with a housing with inside it a drying zone with afirst inlet for compressed gas to be dried, to which a second end ofsaid pressure line is connected in such a way that the full flow rate ofcompressed gas originating from said compressor element is transportedto the drying zone; and whereby said drying zone further comprises afirst outlet for dried, compressed gas to which a discharge line isconnected; whereby in said housing a regeneration zone is also providedwith a second inlet for the supply of used regeneration gas, and asecond outlet for the discharge of the regeneration gas; whereby in thehousing of the drying device a drying agent can be successively movedthrough said drying zone and the regeneration zone; and whereby saidpressure line comprises a heat-exchanger for cooling the compressed gasbefore it enters said drying zone; and whereby, according to theinvention, a first tap-off pipe is connected to said discharge line thatis connected to a cooling inlet of said heat-exchanger, while saidheat-exchanger further comprises a cooling outlet that is connected by asecond regeneration line to said second inlet of the regeneration zone,while the second outlet of the regeneration zone is connected by areturn line to said pressure line, at a point downstream of saidheat-exchanger.

An important advantage of a compressor installation according to theinvention is that for the regeneration of the drying agent is made of apart of the already dried gas that to this end is branched offdownstream of the drying zone, with this part of the gas also heated inan energy-saving way by making use of the compression heat, whereby therelative humidity of the regeneration gas becomes exceptionally low,while the compressor installation also works energy-efficiently byusefully using the discharged compression heat in the heat-exchanger.Indeed, in this way cooling capacity savings are made and no heatingelement has to be provided to obtain a sufficiently low relativehumidity of the regeneration gas for a very good regeneration of thedrying agent.

The present invention also concerns a method for drying compressed gasoriginating from a compressor element, whereby use is made of a dryingdevice provided with a housing inside of which there is a drying zonethrough which the full flow rate of gas to be dried is transported;whereby in said housing also a regeneration zone is provided throughwhich a regeneration gas is simultaneously transported; and whereby thecompressed gas to be dried is cooled in a primary part of aheat-exchanger before entering said drying zone; and whereby, accordingto the invention, a part of the dried compressed gas is branched off atan outlet of the drying zone, and then guided through a secondary partof said heat-exchanger to be heated by means of the compression heat ofthe gas to be dried, before being guided to an inlet of the regenerationzone to serve as regeneration gas therein.

According to a special variant of the method according to the invention,the branched off dried gas is guided parallel through a secondary partof a number of heat-exchangers, whereby each of these heat-exchangerscomprises a primary part that is connected to the outlet of onerespective compressor element from a series of at least two compressorelements connected in series. The invention is not limited as suchbecause all types of heat-exchangers can be used, for example alsoheat-exchangers not provided with a primary part that is connected tothe outlet of a compressor element. Combinations of heat-exchangers arealso possible, with one or more having a primary part connected to theoutlet of a compressor element, while there are also heat-exchangersthat do not have such a connection.

BRIEF DESCRIPTION OF THE DRAWINGS

With the intention of better showing the characteristics of the presentinvention, as an example, without any limiting nature, some preferredembodiments of a compressor installation according to the invention aredescribed, as well as a method according to the invention for dryingcompressed gas, with reference to the accompanying drawings, wherein:

FIGS. 1 to 3 schematically show different embodiments of a compressorinstallation according to the invention; and

FIG. 4 schematically shows an intercooler from FIG. 2 on a larger scale.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first embodiment of a compressor installation 1 accordingto the invention that in this case comprises two compressor elements 2 aand 2 b. The invention is not limited as such, however a compressorinstallation 1 according to the invention can also comprise one or morethan two compressor elements 2 a and 2 b.

The compressor elements 2 a and 2 b are connected to drive means notshown in the figure, for example in the form of one or more motors,turbines, sprocket wheels or suchlike.

In this case the compressor elements 2 a and 2 b form a first lowpressure stage 2 a and downstream thereof a second high pressure stage 2b. Preferably, an intercooler 3 is provided in the connection linebetween the relative compressor elements 2 a and 2 b.

The high pressure compressor element 2 b is provided with an outlet 4for compressed gas to which a first end of a pressure line 5 isconnected.

The compressor installation 1 according to the invention furthercomprises a drying device 6 for compressed gas, with the drying device 6comprising a housing 7 in which a drying zone 8 is located with a firstinlet 9 for compressed gas to be dried and a first outlet 10 for dried,compressed gas, typically at the opposite end of said housing 7.

Said pressure line 5 is connected by its second end to said first inlet9 for compressed gas to be dried.

Said pressure line 5 contains a heat-exchanger 11 for cooling compressedgas that flows from the high pressure compressor element 2 b to thefirst inlet 9 of the drying zone 8. The configuration of theheat-exchanger 11 mentioned is such that cooling takes place before thecompressed gas that originates from the high pressure compressor element2 b enters the drying zone 8.

In this case, but not necessarily, the pressure line 5 is also providedwith an aftercooler 12, that is preferably fitted downstream of saidheat-exchanger 11, meaning according to the flow direction of thecompressed gas, between this heat-exchanger 11 and said first inlet 9 ofthe drying zone.

In said housing 7 of the drying device 6 a drum 13 can be fittedrotatably in the known way, with the drum 13 connected to drive meansnot shown in the figure for allowing this drum 13 to rotate in thehousing 7, for example in the form of an electric motor. The relativedrum 13 contains a regenerable drying agent or so-called desiccantmaterial, such as grains of silica gel, activated alumina or molecularsieve material, or a combination thereof. Obviously, the drying agentcan also be realised in other forms and/or not provided in the drum,e.g., the drying agent is provided in the housing.

Besides said drying zone 8, in the housing 7 of the drying device 6there is also at least a regeneration zone 14.

The drum 13 is configured in the known way such that with rotation thedrying agent can move successively through said drying zone 8 and theregeneration zone 14.

Said regeneration zone 14 is provided with a second inlet 15 for thesupply of a regeneration gas and with an opposite second outlet 16 forthe discharge of used regeneration gas. Used regeneration gas isunderstood to mean gas that, after passage through the regeneration zone14, is contaminated with moisture extracted from the drying agent.

A discharge line 17 is connected to said first outlet 10 of the dryingzone 8 to remove dried, compressed gas, to a user not shown in thefigure, for example in the form of a compressed air network, a pressurevessel or a machine or equipment that uses compressed gas.

According to the invention, to said discharge line 17 a first tap-offpipe 18 is connected which is connected to a cooling inlet 19 of saidheat-exchanger 11, while said heat-exchanger 11 further comprises acooling outlet 20 connected through a second regeneration line 21 tosaid second inlet 15 of the regeneration zone 14.

The relative cooling inlet 19 and cooling outlet 20 in this case formpart of a secondary part of the heat-exchanger 11, the primary part ofwhich is configured such that the compressed gas to be dried is guidedthrough it.

The second outlet 16 of the regeneration zone 14 is connected by areturn line 22 to said pressure line 5, at a point downstream of saidheat-exchanger 11, and in this case, on the part of the pressure line 5that connects the aftercooler 12 to the first inlet 9 of the drying zone8.

In this example the return line 22 also has an additional cooler 23 andpossibly a condensate separator that may or may not be housed in thesame housing as the cooling part of the cooler 23 and that is notvisible in FIG. 1.

In the example in FIG. 1 the connection between the return line 22 andthe pressure line 5 is realised by means of a venturi 24 that is fittedin the pressure line 5 and is provided with a suction opening 25 towhich said return line 22 is connected.

The operation of a compressor installation 1 according to FIG. 1 is verysimple and as follows.

The low pressure stage 2 a sucks a gas or mixture of gases to becompressed such as air. Then a part of the compression heat generated isdischarged by means of the intercooler 3.

After leaving the intercooler 3 the compressed gas flows to the highpressure stage 2 b, where it is further compressed, and then to theprimary part of the heat-exchanger 11. In the relative heat-exchanger11, which at least partly functions as gas-gas heat-exchanger,compression heat is transferred to the gas that enters theheat-exchanger 11 through the cooling inlet 19 and leaves theheat-exchanger again through the cooling outlet 20.

It is clear that the heat-exchanger 11 is assembled such that the gasthat flows through the pressure line 5 is not mixed with the gas that isguided as coolant gas through the secondary side of the heat-exchanger11. In this case the heat-exchanger 11 is configured such that both gasflows flowing through it flow in opposite directions, however this isnot strictly required according to the invention.

The pre-cooled, compressed gas that leaves the heat-exchanger 11 andflows further through the pressure line 5 then arrives in theaftercooler, where further cooling of this gas flow takes place.

Then the cold, compressed gas flows through the venturi 24 and the firstinlet 9 through the drying zone 8, where the moisture present in the gasis absorbed by the drying agent that is present in the drying zone 8 atthe time.

Cold, dry compressed gas then leaves the drying zone 8 through the firstoutlet 10 and flows through the discharge line 17 to the user ofcompressed gas.

According to the invention a part of the cold, dried, compressed gas isbranched off from of the discharge line 17 and then directed through thefirst tap-off pipe 18, to the secondary part of the heat-exchanger 11and more specifically to said cooling inlet 19 to serve there as coolingmedium.

When the gas leaves the cooling outlet 20, its temperature is increasedby absorption of the compression heat generated in the high pressurecompressor element 2 b. As a result, the relative humidity of the gasbranched off through the tap-off pipe 18 will be further decreased in ahighly energy efficient way.

The extra dry gas that flows through the regeneration line 21 is finallyguided through the second inlet 15 to the regeneration zone 14, wherethis gas serves as regeneration gas that will extract moisture from thedrying agent that is in the regeneration zone 14 at the time.

After the regeneration gas has left the regeneration zone 14 through thesecond outlet 16, it flows through the additional cooler 23 and thepossible condensate separator downstream of it, that may but does notnecessarily have to be integrated in the same housing as that of thecooler 23, to the suction opening 25 of the venturi 24.

According to the invention the presence of a venturi is not strictlynecessary, however use can also be made of for example a blower forconverging the regeneration gas that leaves the regeneration zone 14with the flow of warm, compressed gas that flows from the heat-exchanger11 to the drying zone 8 through the pressure line 5.

FIG. 2 shows a variant of a compressor installation 1 according to theinvention in the form of a three-stage machine comprising compressorelements 2 a, 2 b and 2 c fitted in series.

Between the first low pressure stage 2 a and the second pressure stage 2b there is a first intercooler 103, while between the second pressurestage 2 b and the third high pressure stage 2 c there is a secondintercooler 103′.

Downstream of the third high pressure stage 2 c, as with the embodimentin FIG. 1, a heat-exchanger 11 is provided with an aftercooler 12connected in series.

As shown in more detail in FIG. 4, in this example the intercoolers 103and 103′ are realised in two parts, with a first recovery part 103 a anda second cooling part 133 a.

Each respective recovery part 103 a has a primary and a secondary part,whereby the primary part comprises the flow channel for the compressedair to be dried that originates from the compressor element 2 a or 2 blocated immediately upstream of the relative intercooler 103 or 103′,while the secondary part comprises a cooling channel with a coolinginlet 19 a and a cooling outlet 20 a.

In this embodiment the first tap-off pipe 18 is not only connected tothe cooling inlet 19 of the heat-exchanger 11, however also in parallelto the respective cooling inlets 19 a of the intercoolers 103 and 103′.

Similarly, the cooling outlets 20 a, together with cooling outlet 20 ofthe heat-exchanger 11 are connected to the second regeneration line 21.

The second cooling parts 133 a of the intercoolers 103 and 103′ alsocomprise a primary and a secondary part, whereby the primary partcomprises the flow channel for the compressed air to be dried, while thesecondary part comprises a cooling channel through which a cooling fluidcan be guided, preferably, but not necessarily, as a counterflow to thegas flow of the compressed gas to be dried.

The cooling fluid can be a liquid such as water or oil, or a gas ormixture of gases such as air.

In this case the recovery parts 103 a and the cooling parts 133 a arefitted in a shared housing, however these can also be separated fromeach other and realised as separate components. Also according to theinvention, not both intercoolers 103 and 103′ have be connected to thetap-off pipe 18 or the regeneration line 21, however it is also possiblethat only one of these intercoolers 103 or 103′ are connected to therelative lines 18 and 21.

With such a variant the second cooling part 133 a of one or moreintercoolers 103 and/or 103′ can be omitted.

The working of the embodiment as shown in FIG. 2 is essentially similarto the working of the compressor installation 1 in FIG. 1, with the mostimportant difference being that the compression heat from the lowerpressure stages 2 a and 2 b can be utilised to further lower therelative humidity of the gas that is used for regeneration, because thisregeneration gas will act as coolant in the recovery parts 103 a of theintercoolers 103, 103′ respectively and will absorb compression heatthere.

The second cooling parts 133 a can ensure that any excess compressionheat still present in the compressed gas after passing the primary partcan be discharged, such that better compression efficiency can beobtained in the following downstream compression stage.

The residual heat can for example be used for other purposes such asheating sanitary water.

FIG. 3 shows another embodiment of a compressor installation 1 accordingto the invention, whereby in this case three compressor elements 2 a, 2b and 2 c, connected in series, are provided. In this embodiment theconnection between the return line 22 and the pressure line 5 isprovided in a place downstream of the heat-exchanger 11 and upstream ofthe aftercooler 12. In this way no additional cooler needs to beprovided in the return line 22, so costs can be saved.

Although not displayed in the figures, in the housing 7 of the dryingdevice 6 a cooling zone can also be provided, besides said drying zone 8and the regeneration zone 14.

In such a case, in the known way a part of the dried gas at the firstoutlet 10 of the drying zone 8 can be diverted to flow through thiscooling zone and then cool the drying agent that is present in saidcooling zone at the time.

The present invention is by no means limited to the embodimentsdescribed as examples and shown in the drawings but, a compressorinstallation according to the invention with a drying device for dryingcompressed gas can be realized in all kinds of variants, withoutdeparting from the scope of the invention. Similarly, the methodaccording to the invention for drying compressed gas, is not limited tothe variant described above, but can be realized in all kinds ofvariants, without departing from the scope of the invention.

The invention claimed is:
 1. A compressor installation with a dryingdevice for compressed gas, with the compressor installation comprising acompressor element with an outlet for compressed gas to which a firstend of a pressure line is connected; whereby said drying device isprovided with a housing with inside it a drying zone with a first inletfor compressed gas to be dried, to which a second end of said pressureline is connected in such a way that the full flow rate of compressedgas originating from said compressor element is transported to thedrying zone; and whereby said drying zone further comprises a firstoutlet for dried, compressed gas to which a discharge line is connected;whereby in said housing a regeneration zone is also provided, with asecond inlet for the supply of a regeneration gas, and a second outletfor the discharge of the regeneration gas; whereby in the housing of thedrying device a drying agent is provided and whereby said pressure linecomprises a heat-exchanger for cooling the compressed gas before itenters said drying zone, wherein on said discharge line a first tap-offpipe is connected that is connected to a cooling inlet of saidheat-exchanger, while said heat-exchanger further comprises a coolingoutlet that is connected through a second regeneration line to saidsecond inlet of the regeneration zone, while the second outlet of theregeneration zone is connected through a return line to said pressureline, at a point downstream of said heat-exchanger.
 2. The compressorinstallation according to claim 1, wherein said heat-exchanger in thepressure line is provided in a place downstream of said compressorelement and upstream of an aftercooler that is also provided in saidpressure line.
 3. The compressor installation according to claim 2,wherein no cooler is provided in said return line.
 4. The compressorinstallation according claim 1, wherein said return line connects to asuction opening of a venturi fitted in the pressure line.
 5. Thecompressor installation according to claim 1, wherein in said returnline a blower is provided for the convergence of the used regenerationgas with the gas to dry in the pressure line.
 6. The compressorinstallation according to claim 4, wherein said heat-exchanger isprovided upstream of said venturi.
 7. The compressor installationaccording to claim 2, wherein said aftercooler is provided downstream ofthe venturi and upstream of the inlet of the drying zone.
 8. Thecompressor installation according to claim 2, wherein said aftercooleris provided upstream of the venturi and downstream of theheat-exchanger.
 9. The compressor installation according to claim 1,wherein said heat-exchanger is made up of two parts, with a firstrecovery part and a second cooling part.
 10. The compressor installationaccording to claim 9, wherein said heat-exchanger is an intercooler,that is fitted according to the flow of the compressed gas to be dried,between two compressor elements connected in series.
 11. A method fordrying compressed gas originating from a compressor element, said methodcomprising using a drying device provided with a housing within which adrying zone is located through which the full flow rate of gas to bedried is transported; whereby in said housing also a regeneration zoneis provided through which a regeneration gas is simultaneouslytransported; and whereby the compressed gas to be dried is cooled in aprimary part of a heat-exchanger before entering said drying zone;wherein a part of the dried compressed gas is branched off at an outletof the drying zone, and then guided through a secondary part of saidheat-exchanger to be heated before being guided to an inlet of theregeneration zone to serve as regeneration gas therein, wherein thebranched off dried gas is guided parallel through a secondary part of anumber of heat-exchangers, whereby each of these heat-exchangerscomprises a primary part that is connected to the outlet of onecompressor element from a series of at least two compressor elementsconnected in series.
 12. A method for drying compressed gas originatingfrom a compressor element, said method comprising using a drying deviceprovided with a housing within which a drying zone is located throughwhich the full flow rate of gas to be dried is transported; whereby insaid housing also a regeneration zone is provided through which aregeneration gas is simultaneously transported; and whereby thecompressed gas to be dried is cooled in a primary part of aheat-exchanger before entering said drying zone; wherein a part of thedried compressed gas is branched off at an outlet of the drying zone,and then guided through a secondary part of said heat-exchanger to beheated before being guided to an inlet of the regeneration zone to serveas regeneration gas therein, wherein the branched off part of dry gas isguided through the secondary part of a recovery part of a two-partheat-exchanger that also comprises a cooling part.
 13. The methodaccording to claim 12, wherein a separate cooling flow is guided througha secondary part of said cooling part.